1. Field of the Invention
The present invention concerns a display apparatus, and more particularly a display apparatus for converting analog video signals from a host into digital video signals displayed on a liquid crystal display (LCD) panel.
2. Background of the Invention
As the LCD frequently replaces the CRT to display the analog video signals from a computer, there becomes required an apparatus for converting the analog video signals into corresponding digital video signals.
In a conventional LCD video display apparatus, analog RGB video signals, horizontal sync signals and vertical sync signals from a host are input through a connector and amplified by a preamplifier to a TTL level. Then, the amplified analog video signals are converted into corresponding digital video signals and applied to a LCD driver composed of an application-specific integrated circuit (ASIC).
Generally, the maximum level of the video signal input to the LCD display apparatus is about 0.7V, which is amplified by the preamplifier 20 to the TTL level of maximum 5V. However, if video signals of maximum 1.4V are input into such a LCD display apparatus with the input level of 0.7V, the output of the preamplifier becomes 10V at maximum. This causes the generation of saturated digital values (maximum values) for the video signals of more than 0.7V, thereby resulting in distorted images.
U.S. Pat. No. 5,751,261 to Matthew Zavracky et al. and entitled Control System For Display Panels provides an example of a known connector used for supplying the RGB video signals, horizontal sync signals and vertical sync signals from a host computer to a LCD panel.